Polyvinyl acetal silver halide emulsion containing polyvinyl acetal color formers



United States Patent POLYVINYL ACETAL SILVER HALIDE EMULSION SgNTAlNlNG POLYVINYL ACETAL COLOR Joseph De Witt Overman, New Brunswick, N. J assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Application June 23, 1953 .SerialNo. 363,658

13 Claims. (CI. 96-74) In the preparation of multilayer color films utilizing synthetic colloid binding agents for the silver halides, it has been the custom to separately prepare each silver halide emulsion for each respective photographic silver halide emulsion layer. This is inconvenient because it involves a duplication of steps. Thus, a separate operation of grain precipitation and growth, coagulation, washing and redispersion for each of the three emulsions has been practiced. It has been difficult to obtain 1 good seusitometric balance in films made in this manner because the silver halide grains in the respective layers are formed under non-identical conditions.

An object of this invention is to provide a simplified process for the manufacture of diflerentia'lly sensitized polyvinyl acetal emulsions-and emulsion layers for multilayer color films and papers. Another object is to provide a process for the preparation of such emulsions and layers wherein the light-sensitive silver halide grains exhibit similar size distribution in each layer. A further object is to provide a more rapid and efficient manner of preparing the three polyvinyl acetal color forming silver halide emulsions or dispersions for coating multilayer color films. Still other objects will be apparent from the following disclosure. 1

It has been discovered that p-hydroxybenzaldehyde polyvinyl acetals are excellent protective colloids for silver halide grains and that the aqueous silver halide dispersions made with such colloid binding agents can be ripened to the desired grain size distribution, split into portions and each portion mixed with a polyvinyl acetal color-former, and, if desired, other water-soluble, non-color-forming colloids such as polyvinyl alcohol,

partially hydrolyzed polyvinyl acetate, polyvinyl acetals,

etc. Two or more of such portions can be mixed with spectral sensitizing dye or dyes and other emulsion adjuvants to produce aqueous coating compositions suitable for coating as cooperative layers on film base or paper and the silver halide grain size distribution and .history of treatment of the resulting layers will be essentially the same, thus providing good sensitometric balance inthe multilayer photographic element.

The novel process of the invention in its broader aspects comprises-precipitating light-sensitive silver halides in an aqueous solution of a 'p-hydroxybenzaldehyde polyvinyl acetal, allowing the silver halide grains to grow (ripen?) to the desired extent, removing the water-soluble salts, if desired, dividing the resulting aqueous dispersion into portions, admixing with respective separated pordons a different polyvinyl acetal color-former capable of yielding an azomethine or quinoneimine dye upon color couplingdevelopment of the exposed silver halide grains 7 layers. .For example, the layers may .contain from to 50%- by weight of a water-soluble or 'hydrophilic polyvinyl alcohol .or a partially hydrolyzed polyvinyl ester or a polyvinyl acetal, e. g., the sodium o-sulfobenzaldehyde acetal of polyvinyl alcohol and .p-hydroxybezaldehyde acetal -ofpolyvinyl alcohol. They'are then coated as superimposed layers on a suitable sheet support such as a film base or paper .base. A blue light absorbing medium is provided either as a yellow dye or pigment in the blue sensitive layer or as a separate filter layer between the upper blue sensitive layer and the lower layers to prevent-blue :light from exposing any spectrally sensitized layer.

In a preferred aspect of the invention, a mixture of light-sensitive silver halides are precipitated in an aqueous ethanol solution of a p-hydroxybenzaldehyde polyvinyl {acetal colloid, the silvero halide grains permitted "to ripen, the dispersions 'of the silver halides in said acetal coagulated, the :coagulated dispersion washed free from dissolved inorganic salts, the washed coagulate-redissolved in aqueous ethanol and admixed, if desired, with more of said acetal, or other non-color 'formingcolloid and the resulting solution divided into portions, each portion admixed with an-aqueous ethanol solution of a diiterent polyvinyl acetal eo'lort'ormer capable of-yieldin'g a quinoneimine or azomethine dye upon color-coupling development :of exposed silver halide grains, andadmixing with two or more of such portions an appropriate spectral sensitizing dye and other emulsion adjuvants respectively, so that the resulting emulsions have-strong sensitivity in difierent primary :color regions of the spectrum. .The resulting dispersions are thencoated'as superposed layers on a suitable sheet support such as :a film .base or paper base.

The -.p-.hydroxybenzald.ehyde polyvinyl acetals useful in accordance with the invention are vl'rydrophilic colloids which contain a large number of :intralinear vinyl alcohol .hyde polyvinyl acetals are .non-co1or.-forming polyvinyl acetals.

The polyvinyl acetals described in .the next preceding paragraph can be prepared by any conventional acetalization reaction from the stated aldehydes or their ethylene glycol or dimethyl or diethyl acetals and an acid catalyst,

preferably in an ethylene glycol medium. Suitable procedures are described in Dorough and McQueen U. S. Patent 2,310,943, Martin'U. S. Patent 2,513,189, and German Pa ent =643..6..:5.0- They can .be .tnade from polyvinyl alcohol or partially hydrolyzed polyvinyl esters :and hydrolyzed olefine/vinyl acetate copolymers and may conexamples are 3 tain small amounts of other non-color coupling groups as taught in said U. S. patents.

The polyvinyl acetal color formers which can be blended with the p-hydroxybenzaldehyde polyvinyl acetals are essentially colorless, synthetic polymers which have protective colloid properties and form waterpermeable layers. They contain'a plurality of aliphatic hydroxy groups, usually in the form of vinyl alcohol units (CH -CHOH-groups) in the polymer chain, as the predominant hydrophilic groups and have as an integral part of their molecular structure color-former nuclei as described in the following paragraph. They also preferably contain solubilizing groups from acetalization with an aldehyde containing such a group, e. g., 'SO Na and CO' Na. These synthetic color forming, waterpermeable colloids contain thefollowing structural units:

nuclei need not be directly attached to the -.-CH groups p but may be part of a radical or group which is so attached. The color former nuclei have as the active group a structure whichmay be represented by .the formula:

wherein X is H--- or RHN, wherein R is hydrogen or an aliphatic group and n is 0 or 1. The free or dangling valences may, of course, be satisfied by various atoms or groups, e. g., hydrogen, halogen, carboxylic or sulfonic acid groups and their derivatives, fused rings, alkyl; aryl, alkoxy, aryloxy, etc. The hydrogen atom in the formula may be replaced by groups readily displaced in the coupling reaction, e. g., halogen atoms, carboxylic or sulfonic acid groups. This active group is found in the active methylene color formers or dye intermediates and in-aromatic hydoxyl and. amino compounds and include the reactive ethanol, aminoethyl, 4-hydroxyand 4-amino-1,3-butadienyl groups. These groups occur in phenols, naphthols, aromatic amines, acylacetamides, betaketoesters, pyrazolones, homophthalimides, cyanoacetyl compounds, etc. The reactive ethenol group as represented by HO=7H occurs in phenols and naphthols which couple in the ortho position, and in the alkali soluble or enol form of most active methylene dye intermediates or color formers. These active methylene groups (CH have a hydrogen rendered mobile by the proximity of certain unsaturated groups, for example,

tween two such groups, e. g.,

--COCH:CO, OOCH:CN, -COOHZ('J= in a cyclic or acyclic system. The enol forms of these centipoises) e and I HOC=CHCII=N- respectively. 7

The reactive aminoethenyl group HO( )=c't(J=CH and RHN('3=C'J- 3=CH occur in phenolic, naphtholic and aromatic amino compounds which couple in the para position.

Among the specific polyvinyl acetal color formers which can be used in accordance with the invention are those described in the following U. S. patents: 2,310,943; 2,320,422; 2,380,032; 2,380,033; 2,397,864; 2,397,865; 2,415,381; 2,422,680; 2,423,572; 2,464,597; 2,465,067; 2,472,666; 2,472,910; 2,472,911; 2,472,913; 2,473,403; 2,476,988; 2,477,462; 2,513,189; 2,513,190; 2,538,257; 2,562,527; 2,562,528; 2,575,182; and in U. S. applications Martin Ser. No. 172,191, filed July 5, 1950, now U. S. Patent 2,680,730, and Martin Ser. No. 172,192, filed July 5, 1950, now U. S. Patent 2,680,731. These hydroxyl polymer color formers or vinyl alcohol polymers may contain a substantial proportion of sodium o-sulfobenzald ehyde acetal or equivalent groups as taught in said patents. In general, the linear unit CH CHOH-- should represent at least 50% ofthe polymer chain, between 1 and 35 color-former nuclei should be present for each chain atoms and the polymer chain be in excess of 200 carbon atoms. Of course, minor amounts of lower molecular weight polymers may be present. 7

The invention will be further illustrated but is not intended to be limited by the following examples in which the preparation, coating, etc. of the photographic ele ments is carried out in the substantial absence of radiation which would produce exposure of the materials in process. The polyvinyl alcohol used in these examples is, unless otherwise stated, medium viscosity completely hydrolyzed (viscosity of 4% aqueous solution at 20 C., 15 to 20 7 Example 1 One and one-half (1.5) mols of silver bromide are precipitated under. conditions known to give a low contrast emulsion, inan aqueous ethanol solution containing as a protectivecolloid 40 grams of an acetal made by reacting .on a weight basis 100 parts polyvinyl alcohol, 10 parts p-hydroxybenzaldehyde and 2 parts sodium benzaldehyde o-sulfonate. After the completion of a 75 minute ripening period at F., the silver halide polymerdispersion ,is coagulated, washed with water to remove soluble salts and redispersed in a solution of 28% ethanol by weight in water, and the pH adjusted between the limits 8.9 to 9.1 after which an additional 40 grams of the same mixed polyvinyl acetal is added. This redispersed emulsion is divided into three parts in preparation for coatingQOne part is admixed with 460 grams per mol ofsilver of a yellow color-forming polyvinyl acetal made by reacting on a weight basis 100 parts of polyvinyl alcohol, 17 parts m-benzoylacetamidobenzaldehyde ethylene glycol acetal, and 0.8 part sodium benz- ,alcohol, 20 parts M-(3-methylsalicylamido)benzaldehyde .ethylene glycol acetal and LS parts sodium .benzaldehydeo-snlfonate as described in U. 5. Patent 2,489,655; the

third part is admixed with tartrazine C. I. 6 40) ai1tl 564 grams per mol of silver of a magenta color-forming polyvinyl acetal made by reacting on a weight basis 100 parts of poly inyl alcohol, .18 parts 2-eyanoasetyl-3- phenyl-S-benzofuraldehyde "ethylene ,glycol acetal,and11 jpart sodium benzaldehyde-o-sulfonate as .described in Martin U. .S. patent application- S. N. 193,291,1-filed October 31, 1950, U. ;S. Patent 2,680,732. The three 'emulsions are modified by the addition of a sulfur sensitizer; the emulsion containing yellow color former is sensitized to ,green by theaddition ,of a .symmetrical oxycarbocyanine dye and the emulsion containing cyan color forming polymer is sensitized to :red light by an unsymmetrical thiocarbocyanine dye which confers no sensitivity in the green region of the spectrum, and the three emulsions are then separately-digested and prepared for coating.

A multilayer negative film is then made by coating the threeemulsions on.0.005 vinch thick cellulose triacetate film base to which .-have been applied, in order, :two (thin nitrocellulose layers and an emulsion substratum layer separatorlayer (12 mg. per sq. dm.?) ofpolyvinylalcohol- 'on which :is coated the redsensitized =cyan color-orming emulsion to a silver halide coating weight of 2-8 mg. per sq. dm. Next, there is appliedanother thin ,polyvinyl alcohol separator layer :over which is coated the blue .sensitized magenta :color-formingemulsion so as :to give a silver halidecoating weight-of-22.mg. ,per sq. dm.

The completed film is:exposed to light from blaekand "white color component-positives comprising the blue,

green and red records of a'multicolorscene and processed to a duplicating color negative as described vin the J ournalofthe Society of Motion Picture :and Television Engineers, November 1950, pp. 455-476.

Example II A redispersed emulsion was prepared at pH 9 and :with 30% by weight of ethanol in the aqueous solvent medium as described in Example I but using a polyvinyl 'acetal prepared with 12 parts of p-hydroxybenzaldehyde and no sodium benzaldehyde o-sulfonate. This redispersed emulsion was divided into portions, one portion was used in the preparation of .a magenta and another in the preparation of a cyan emulsion as described :in Example I. The emulsions were coated on separatefilm bases. The coated v-films were evaluated by giving them step wedge exposures through appropriate filters on a laboratory sensitometer (non-intermittent intensity scale ,sensitometer employing :a neutral density wedge .fol. modulation of printing light), and the exposed films processed as inExample I, and reading the .sensitometricstrips 80 obtained -.on a precision iutegrating sphere densitometer Frayne, 6., with Crane, G.1R., Journal of the Society .of Motion Picture and Television Engineers, vol. 35, No. 2, August 1950, p. 184) and 'a modification of this densitorneter (A. C. Lapsley and J. P. Weiss, Journal of the Society of Motion Picture and Television Engineers,

- vol. :56. January 1951, p. 23 This evaluation demonstrated that the films had satisfactory speed and gamma .andsatisfactory grain size distribution for use in a color duplicating negativeof the type-described in Example 1.

Example III o-sulf onate. A film is made as in Example I except the polyvinyl alcohol separator layer between the magenta .andcyan .layers contains yellow colloidal silver (to augmentzthe filtering .of blue .light by the vtartraziue :dye).

Evaluation as described .in Example I demonstrated that .the filmhad uniform grain size distribution .in all layers and goodsensitometric balance-and was satisfactory asa motion picture color duplicating negative.

Example IV A multilayer film is prepared as in Example III with the precipitating and ripening conditions adjusted :to give high contrast silver halide. When this film is exposed to appropriately colored light through black and white component negatives comprising the blue, green and red records of a multicolor scene and processed .to a color positive'zas described in the lournal of the Society of Motion Picture and Television Engineers, November .1950, ,pp. 455-476, a color positive of excellent color .qualityis-obtained. Alternatively, the film-may be exposed to :a color negative such as is described in Example .I and processed to produce a color print of excellentquality.

- Example V P-hotographic emulsions are prepared as described in Example I except that they are sensitized and coated as follows: The cyan color-forming emulsion, sensitized to red 'light, is coated on the treated base so as to give -a=silverhalidecoating weight of '50 mg. per sqvdm. On that emulsion is coated -a thin layer of polyvinyl alcohol;

then the green sensitized magenta color-"forming emulsion is -coated over the separator layer so as to give a silver shalide coating weight of 23 mg. 'per sq. dm. Next there is applied another polyvinyl alcohol 'layer over which is coated the blue sensitive yellow color-forming emulsion (containing tartrazine as a filter dye) so as to give a silveryhalide coating weight of 22 mg. per sq. dm. Evalua- 'tion as described in Example II demonstrated :that the complete multilayer film had satisfactory speed, gamma and color balance for use as a motion picture color duplicating negative.

Example VI Photographic emulsions are prepared as described in Example 1, except that they are sensitized and coated base :described above so .as to give a silver halide coat- :ing weight of 35 mg. per sq. dm. On this emulsion is coated a thin separator layer of polyvinyl alcohol; :then the red sensitized cyan color-forming emulsion "is coated over the separator layer so as to give a silver .halide coating weight of 37 mg. per sq. dm. Next, there is applied another thin separator layer of polyvinyl alcoholiover whichis coated the blue sensitive yellow colorforming emulsion (containing tartrazine as a 'filterdye) at a silver bromide coating weight of 35 mg. per sq.:dm. Evaluation as described in Example II demonstrated that the complete multilayer film had satisfactoryspeed, gamma and color balance for use as a motion picture color duplicating negative.

Example VII A redispersed emulsion was prepared at pH 9 and .with 28% byweight of ethanol in the aqueous solvent medium as described in Example I but using apolyvinyl .acetal prepared with 8 parts of p-hydroxybenzaldehyde and 2 parts of "benza'ldehyde o-sodium sulfonate. This .redispersed emulsion was used in the preparation of a cyan color-forming emulsion as described in Example I.

"The resulting emulsion was coated on film base as de scribed in Example I and evaluated asdescribed in 'Example II. The sensitometric results vindicated that the emulsion had satisfactory speed and contrast for use in with 28% by weight of ethanol in the aqueous solvent medium as describedin Example I but using a polyvinyl acetal prepared with parts of p-hydroxybenzaldehyde and 4 parts of sodium benzaldehyde o-sulfonate. This redispersed emulsion was used in the preparation of a emulsion. had satisfactory speed and contrast for use in' a duplicating color negative film.

Example IX 7 A redispersed emulsion is prepared as in Example I, using precipitating and ripening conditions adjusted to give highrcontrast silver'bromide. This redispersed emulsion is divided into three parts. One part is mixed with 300 grams per mol of silver of a yellow color-forming polyvinyl acetal made by reacting on a weight basis 100 parts of polyvinyl alcohol, 61.5 parts m-benzoylacet-' amidobenzaldehyde ethylene glycol acetal and 29 parts of sodium benzaldehyde o-sulfonate as described in U. S. Patent 2,513,190, and 200 grams of polyvinyl alcohol; another part is admixed with 300 grams per mol of silver of cyan color-forming polyvinyl acetal made by reacting on a weight basis 100 parts polyvinyl alcohol, 60 parts m-(3-methylsalicylamido)benzaldehyde ethylene glycol acetal and 30 parts sodium benzaldehyde o-sulfonate, as described in U. S. Patent 2,489,655, and with 200 parts of polyvinyl alcohol, while the third part is admixed with 300 grams per mol of silver of a magenta color-forming polyvinyl acetal made by reacting on a weight basis, 100 parts of polyvinyl alcohol, 60 parts of 2-cyanoacetyl-3- phenyl-S-benzofuraldehyde ethylene glycol acetal and 20 parts sodium benzaldehyde o-sulfonate as described in U. S. application Ser. No. 193,297, filed October 31, 1950 now U. S. Patent 2,680,732, and with 200 parts of polyvinyl alcohol. The three emulsions are modified by the addition of a sulfur sensitizer. The emulsion containing the magenta color-former is sensitized to green by the addition of a symmetrical oxycarbocyanine dye and the emulsion containing cyan color-forming polymer is sensitized to red light by an unsymmetrical thiocarbocyanine dye which confers no sensitivity in the green region of the spectrum and the three emulsions are then separately digested and prepared for coating. A multilayer negative film is prepared by coating on a base such as is described in Example I, the red sensitized cyan color-forming emulsion. On this emulsion layer is coated the green sensitized magenta color-forming emulsion and there is next applied a layer of colloidal silver having an optical density to blue light of 1.5, over which there is coated the blue-sensitive yellow color-forming emulsion. The com pleted film is exposed to light from a color negative having the same conventional layer arrangement of colorformcr to emulsion sensitivity and processed as described in Example IV to a color-positive of excellent color quality.

The silver halides can be precipitated in the foregoing emulsions in the usual manner by dissolving a soluble, ionizable halide, e. g., sodium, potassium, or ammonium chloride, bromide or iodide, or mixtures thereof in Water and by dissolving separately in water a soluble, ionizable silver salt, e. g., silver nitrate, silver sulphamate, silver acetate or silver citrate or mixtures of two or more such compounds. The two solutions are admixed with the solution of simple or mixed p-hydroxybenzaldehyde polyvinyl acetal in any order and in one or several portions depending on the particular photographic qualities desired.

After redispersion of the coagulated silver halide dispersions in the p-hydroxybenzaldehyde 'polyvinylacetals the emulsions can be modified before or after addition with the color-formingpolyvinyl acetal by the addition of general emulsion sensitizers, e. g., allyl thiourea,.

plienyl isothiocyanate, sodium thiosulfate, and allyl isochromium compounds or other emulsion adjuvants.

' Other water or water-alcohol soluble, non-color-forming colloids such as polyvinyl alcohol, partially hydrolyzed polyvinyl acetate, partially or completely hydrolyzed copolymers of vinyl acetate or acetals of these with aldehydes free of groups which form colored products in the color development reaction, esters or ethers of cellulose or starch, polymers or copolymers of acrylic or 'methacr'ylic acid, etc., can be added as desired to improve the solution viscosity, increase the film thickness or improve film permeabilityJ In addition to the solubilizing aldehydes" of the examples, other aldehydes containing ionic groups can be used in the polymer, such as ophthalald'ehydic acid, sodium benzaldehyde-m-sulfonate, p-carboxyphenylbenzaldehyde, glyoxylic acid, succinaldehydic acid, adipaldehydic acid, or 3-formylcyclohexaneoic acid' can be used. Also, minor amounts of acetal groups prepared from benzaldehyde, acetaldehyde, furaldehyde, butyraldehyde, etc. can be included in the polymers as desiredto modify the solubility and permeability characteristics.

The p-hydroxybenzaldehyde simple and mixed acetals, used in accordance with the invention, have the desirable property of being halogen acceptors and result in silver halide color-forming emulsions of high speed.

An advantage of this invention is that it provides a simple and practical method of preparing a plurality of silver halide polyvinyl acetal color-forming emulsions.

-A further advantage is that multilayer papers and films coated from'the emulsions have uniform grain size distribution. Afurther advantage resides in the fact that the multilayer films and papers made from the emulsions have good sensitometric balance. A still further advantage accrues from the economies of operation resulting from the use of a single emulsion formulation for all layers of a multilayer film or paper. Further economies may result from the use of continuous emulsion manufacture techniques.

What is claimed is 1. A process which comprises precipitating light-sensitive silverhalides in an aqueous solution of a non-colorforming polyvinyl acetal taken from the group consisting of simple acetals of polyvinyl alcohol with p-hydroxybenzaldehyde and mixed acetals of polyvinyl alcohol with p-hydroxybenzaldehyde and an aldehyde containing a solubilizing group taken from the class consisting of aliamino, secondary amino and OH groups and n is a numconsisting of quinoneimine and azomethine dyes and containing in one of its tautomeric forms as an integral part of the, molecule an active coupling group of the structure where X is' taken from the group consisting of primary ber taken from the group consisting of 0 and 1.

2. A process which comprises precipitating light-sensiltive silver halides in an aqueous solution of a hydrophilic macromolecular mixed acetal of, polyvinyl alcohol with fphydroxyhenza-ldehyd'e vand ran aldehyde containing a isohlbilizing :group taken from the zclasstconsisting :o'f aligihatic and .saronratic :carboxyiic :zrcids sand "sulfonic acids sand their water-soluble :salts, the :hydroxyl, :c'arboxylic and :sultonic groups :being the -:so1e substituent :group attachedto thehydrocarbon nucleus ofsaidzaldehydes,said polyvinyl lacetals containing .a large "number of :intralinear -aCH CI-IOH groups. allowing thesilvenhalide crystals toripen :a-ndadmixingwithrthetdispersion a waterpermeable colloid at least :a partgof "which .is 1 a polyvinyl iacetal color :tormer :capable :of :forming :upon color cou- :pling :development of :an :exposed silver salt image a idye'ztaken :from'ithe agrouprconsistingiof qninoneiminezand azomethine dyes and :containing'in'oneiof :its :tautomeric :forms :as an integral part :of ith'e im'olecule an :active coupling groupofthestructure ,wheret'X is taken from the .group consisting :of primary and, their water-soluble salts, the hydroxyl, carboxylic,

and sulfonic groups being the sole substituent group attached to the hydrocarbon nucleus of said aldehydes said polyvinyl acetals containing a large number of intracharacter; allowing the silver :halide @crystals :to ripen, dividing the resulting aqueous dispersion 'into portions, and admixing ta different polyvinyl ia'cetal color former capable :of forming :upon :color coupling :development of an ex-poseclsilver j-salt image :afdye taken ifrom'the group qconsistingof quinoneimine aandzazom'ethinezdyes and conraining in one of its *tautomeric forms zas :anintegral part ,of the molecule an active coupling agroup ofrthestruc'ture where X is taken from the group consisting of primary amino, secondary amino and OH groups and n is a number taken from the group consisting of and 1 with each of more than one of such portions.

5. A process which comprises precipitating light-sensiitive silver halidesfin an aqueous solution .of anon-colorforming polyvinyl acetal taken from the group consisting of simple acetals of polyvinyl alcohol with p-hydroxybenzaldehyde and mixed ,acetals I of polyvinyl alcohol with p-hydroxybenzaldehyde and an aldehyde containing a solubilizing group taken from the class consisting of alilphatic and aromatic carboxylic acids and sulfonic acids and their water-soluble salts, the hydroxyl, car boxylic and :sulfonicgroups .being thesole substituent group attached to the :hydrocarbon nucleus of said aldehydes, said polyvinyl a'ceta'ls containing a large number of intralinear -CH CHOH- groups and being hydrophilic in character; allowing the silver halide crystals to ripen, removing the water-soluble salts, dividing the resulting aqueous dispersion into portions, and admixing a ditferent polyvinyl acetal color former capable of forming upon color coupling development of an exposed silver salt image a dye taken from the group consisting of quinoneimine and azomethine dyes and containing in one of its tautoimericzforms asieui integralrpart of :the rmoleeulelan acti-ve coupling. group :ofathe structure where X is taken from the group consisting of primary amino, secondary ,aminosand OH groups and nis a number taken fromtthegroupiconsisting of 0 and 1 with each a of more thantionezofsuch,portions.

-.6. A process which comprises precipitating light-sensitive tsilverahalides in: an aqueous solution of a "non-color- .lformingpolyuinyl :acetal [taken from tthe group consisting of :simple racetals of ,polyvinyl alcohol with p-hydroxy- Ibenzaldehyde andmixed acetals. of polyvinyl alcohol with p hydroxyben-zaldehyde and an 'zaldehyde containing a solubilizing group taken from the class consisting ofraliphatic and aromatic carboxylic acids and sulfonic-acids and their water-soluble salts, the hydroxyl, carboxylic and sulfonic groups "being-the sole substituent group attached ,to the hydrocarbon nucleus of said aldehydes, said {polyvinyl acetals containing alargenumber of intralinear -CH "CHQHigroups and being ,hydrophilic in character; allowing the silver halide crystals to ripen, dividing the *restiltingeaqueolls dispersion into portions, admixing a 'ditterent polyvinyl acetal colloid color former capable of forming upon color coupling development of an exposed silverlsalt image a dye taken from the group 7 consisting of guinoneirnine and azomethine dyes and containingin one of its *tautomeric forms as an integral part "of ;the nrolecule an active coupling group of the structure where X is taken item the group zconsisting of primary amino, secondary amino and OH groups and n is a number taken from'the ,group consisting .of band l rwithreach of more than (meet such portions, .and separately coating the portions .asflayers -on,a sheetsupport.

7. Aprocess which comprises precipitating ,lightesensi- 'tive silver halides in an aqueous solution of a non-.co'lorforming polyvinyl acetal taken ,from the ,group consisting of simple acetals of polyvinyl alcohol with .p-hydroxybenzaldehydeand mixed acetals oflpo'lyvinyltalcoho'l with p-hydroxybenza'ldehyde and an aldehyde containing a solubilizing group taken \from .the class vconsisting of aliiphatic and aromatic car'b'oxyilic .acids and sulfonioacids and their water-soluble salts, the ;hydroxyl, .carboxylic and sulfonic groups 'being the sole substituent group :at-

tached ,to the hydrocarbon nucleus of said aldehydes, said polyvinyl acetals containinga lange numberofintralinear -,C.H -CH.OH,groups and being hydrophilic in character; allowing the .silver halide crystals -.to ripen,

removing the water-soluble salts, dividing the resulting aqueous dispersion into portions, admixing .a different polyvinyl acetal colloid color .former .capableof .forming upon color couplingidevelopment ofan ,exposedsilverzsalt image a dye taken irom the group consisting of quinoneimine and azomethine dyes and containing in one of its tantomeric Iformsas an integralpart of the molecule an active :coup'ling group of .thestructure where X is taken from the ,group -.consisting :uf primary amino, secondary amino and OH groups :and 11 is a number taken from the group consisting of 0 and 1 with each of more than one of such portions, and separately coating the portions=as layers on a sheet support.

8. A process which comprises precipitating a mixture of light-sensitive silver halides in an aqueous solution of a non'color-forming polyvinyl acetal taken from the group consisting of simple acetals of polyvinyl alcohol with p-hydroxybenzaldehyde and mixed acetals of polyvinyl alcohol with p-hydroxybenzaldehyde and an aldehyde containing a solubilizing group taken from the class consisting of aliphatic and aromatic carboxylic, acids and sulfonic acids and their water-soluble salts, the hydroxyl, carboxylic and sulfonic groups being the sole substituent group attached to the hydrocarbon nucleus of said aldewhere X is taken from the group consisting of primary amino, secondary amino and OH groups and n is a number taken from the group consisting of and l with each of three of said portions, adding a different spectral photographic sensitizing dye to each of two of such portions, and separately coating the portions as layers on a sheet support.

9. A process as set forth in claim 8 wherein the polyvinyl acetal color formers are respectively capable of forming a dye taken from the group consisting of quinoneimine and azomethine dyes and each color former contains in one of its tautomeric forms as an integral part of the molecule an active coupling group of the structure where X is taken from the group consisting of primary amino, secondary amino and OH groups and n is a number taken from the group consisting of 0 and 1 and said layers are sensitive to light of three difierent primary color regions of the spectrum.

10. A process which comprises precipitating a mixture of lightsenstive silver halides in an aqueous solution of a non-color-forming polyvinyl acetal taken from the group consisting of simple acetals of polyvinyl alcohol with 'p-hydroxybenzaldehyde and mixed acetals of polyvinyl alcohol with p-hydroxybenzaldehyde and an aldehyde containing a solubilizing group taken from the class consisting of aliphatic and aromatic carboxylic acids and sulfonic acids and their water-soluble salts, the hydroxyl, carboxylic and sulfonic groups being the sole substituent group attached to the hydrocarbon nucleus of said aldehydes, 'said polyvinyl acetals containing a large number of intralinear CH -CHOH-- groups and being hydrophilic in character; allowing the silver halide crystals to ripen, dividing the resulting dispersion into portions, admixing an aqueous solution containing a yellow polyvinyl acetal color former with one portion, a magenta polyvinyl acetal color former with another portion and a cyan polyvinyl acetal color former with a third portion, each of said color formers being capable of forming upon color coupling development of an exposed silver salt image a dye taken from the group consisting of quinoneimine and azomethine dyes and containing in one of its tautomeric forms as an integral part of the molecule an active coupling group of the structure where X is taken from the group consisting of primary 7 amino, secondary amino and OH groups and n' is a number taken from the group consisting of 0 and 1, adding a sensitizing dye which confers red but no green sensitivity to tone of such emulsions, adding a sensitizing dye which confers green sensitivity to another of such emulsions and coating such emulsions as superposed layers i on a support with a yellow light absorbing stratum disposed between the blue-sensitive silver halide emulsion 10 layer and the red and green-sensitive layers.

11. A process as set forth in claim 10 wherein each of said polyvinyl acetal color formers is a mixed acetal having hydrophilic properties and contains acetal groups from sodium benzaldehyde o-sulfonate.

12. A photographic composition comprising an admixture of a dispersion of light-sensitive silver salts in a non-color-forming polyvinyl acetal taken from the group consisting of simple acetals of polyvinyl alcohol with p-hydroxybenzaldehyde and mixed acetals of polyvinyl alcohol with p-hydroxybenzaldehyde and an aldehyde containing a solubilizing group taken from the class consisting of aliphatic and aromatic carboxylic acids and sulfonic acids and their water-soluble salts, the hydroxyl,

carboxylic and sulfonic groups being the sole substituent group attached to the hydrocarbon nucleus of said aldehydes, said polyvinyl acetals containing a large number of intralinear CH --CHOH-- groups and being hydrophilic in character; and a hydrophilic polyvinyl acetal color former capable of forming upon color coupling development of an exposed silver salt image a dye taken from the group consisting of quinoneimine and azomethine dyes and containing in one of its tautomeric forms as an integral part of the molecule an active coupling group of the structure where X is taken from the group consisting of primary amino, secondary amino and OH groups and n is a number taken from the group consisting of 0 and 1.

'13, A composition as set forth in claim 12 wherein 1 each of said polyvinyl acetal color formers is a mixed acetal having hydrophilic properties and containing acetal groups from sodium benzaldehyde o-sulfonate each of said color formers being capable of forming upon color coupling development of an exposed silver salt image a dye taken from the group consisting of quinoneimine and azomethine dyes and containing in one of its tautomeric forms as an integral part of the molecule an active coupling group of the structure where X is taken from the group consisting of primary 5 amino, secondary amino and OH groups and n is a number taken from the group consisting of 0 and 1.

U S DEPARTMENT OF COMMERCE PATENT- OFFICE CERTIFICATE OF CORRECTION Patent NO- 2,828,205 Joseph De Witt Overman March 25, 1958 It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Let oers Patent should read as corrected below.

Column 2, line 15; for "bezalgie hylf" read benzaldehyde column 3, line 52, for "hydoxyl" read hydroxy'l line 53, for aminoethyl" read aminoethenyl column 8, line 3, for "benzatriazole" read benzotriazole Signed and sealed this 27th day of May 1958.

(SEAL) Attest:

KARL H. vAXl-INE ROBERT C. WATSON Attesting Officer Cannissioner of Patents 

6. A PROCESS WHICH COMPRISES PRECIPITATING LIGHT-SENSITIVE SILVER HALIDES, IN AN AQUEOUS SOLUTION OF A NON-COLORFORMING POLYVINYL ACETAL TAKEN FROM THE GROUP CONSISTING OF SIMPLE ACETALS OF POLYVINYL ALCOHOL WITH P-HYDROXYBENZALDHYDE AND MIXED ACETALS OF POLYVINYL ALCOHOL WITH P-HYDROXYBENZALDEHYDE AND AN ALDEHYDE CONTAINING A SOLUBILIZING GROUP TAKEN FROM THE CLASS CONSISTING OF ALIPHATIC AND AROMATIC CARBOXYLIC ACID AND SULFONIC ACIDS AND THEIR WATER-SOLUBLE, SALTS, THE HYDROXYL, CARBOXYLIC AND SULFONIC GROUPS BEING THE SOLE SUBSTITUENT GROUP ATTACHED TO THE HYDROCARBON NUCLEUS OF SAID ALDEHYDES, SAID POLYVINYL ACETALS CONTAINING A LARGE NUMBER OF INTRALINEAR -CH2-CHOH- GROUPS AND BEING HYDROPHILIC IN CHARACTER; ALLOWING THE SILVER HALIDE CRYSTAL TO REPEN, DIVIDING THE RESULTING AQUEOUS DISPERSION INTO PORTIONS, ADMIXING A DIFFERENT POLYVINYL ACETAL COLLIED COLOR FORMER CAPABLE OF FORMING UPON COLOR COUPLING DEVELOPMENT OF AN EXPOSED SILVER SALT IMAGE A DYE TAKEN FROM THE GROUP CONSISTING OF QUNIONEIMINE AND AZOMETHINE DYES AND CONTAINING IN ONE OF ITS TAUTOMERIC FORMS AS AN INTEGRAL PART OT THE MOLECULE AN ACTIVE COUPLING GROUP OF THE STRUCTURE 